1. A method for improving the friction performance of a graphite material and a preparation method thereof are characterized by comprising the following steps:

(1) and (4) preparing an impregnation liquid. Dissolving boric acid in solvent such as distilled water or absolute ethyl alcohol to prepare boric acid high-concentration solution as impregnation liquid;

(2) and (4) pretreatment of graphite flakes. Cleaning the surface of a graphite flake, and placing the graphite flake in an incubator for drying, wherein the drying temperature is 70-100 ℃, and the drying time is 2-5 hours;

(3) impregnation of graphite sheets: placing the pretreated graphite flakes in an impregnation kettle, pouring high-concentration boric acid impregnation liquid into the impregnation kettle to completely immerse the graphite flakes, fully stirring, standing, keeping the distance between the graphite flakes above 5 mm, and sufficiently impregnating for a long time;

(4) the impregnation solution is evaporated. Keeping the temperature at normal pressure or below 0.5MPa and normal temperature or low temperature for 2-20 hours, taking out the impregnated graphite flake after no obvious liquid exists in the impregnation kettle, and cleaning the surface;

(5) and (3) drying: and (3) putting the impregnated graphite flake into an incubator, setting the temperature to be 40-80 ℃, and carrying out heat preservation and drying.

2. The method for preparing an impregnation fluid as claimed in claim 1, wherein: the main raw material of the impregnation liquid is boric acid, and the mass ratio of the boric acid to distilled water is 1: 4-18, wherein the mass ratio of the absolute ethyl alcohol to the absolute ethyl alcohol is 1: 3 to 14.5.

3. In the preparation of impregnated graphite sheets as claimed in claim 1, characterized in that: (3) the above-mentioned (5) can be realized at normal temperature (25 ℃) or low temperature, and the impregnation step can be repeated to enhance the impregnation effect.

4. In the impregnation vessel of the preparation impregnation apparatus as claimed in claims 3 and 4, characterized in that: the dipping equipment has low requirement, the existing container can be used for dipping according to actual conditions, and the dipping equipment can be small enough to be easily obtained containers such as beakers and flasks and large enough to be large-scale equipment such as reaction kettles and storage tanks.

Background

Graphite has the properties of low density, high temperature resistance, self lubrication, corrosion resistance and the like due to the space structure of close stacking of sheets, so that the graphite is used as a sealing ring material in mechanical sealing. The mechanical seal is a rotary end face seal and is widely applied to various rotary equipment such as pumps, compressors, kettles and the like. The sealing end face has relative friction while playing a sealing role, and the friction working condition of the sealing end face is also complicated and changeable due to different use occasions, such as high temperature and high load working conditions. Meanwhile, the friction of the mechanical seal ring of the rotating shaft equipment is very frequent, and the friction performance of the end face sealing material has obvious influence on the energy consumption of the equipment and the service life of the mechanical seal.

The graphite used in the occasions of mechanical sealing and the like is generally artificial graphite, the artificial graphite has defects in strength because of pores generated on the graphite structure due to the manufacturing process of the artificial graphite, and the graphite is easy to oxidize at high temperature (above 1000 ℃), so that the mechanical property, the friction property, the temperature resistance and other properties of the graphite are improved by adopting an impregnation method in industry. Chinese patent CN102775991A, an immersion type antioxidant liquid for improving the high-temperature oxidation resistance of graphite products and an application method thereof, discloses an immersion type antioxidant liquid for improving the oxidation resistance of graphite at high temperature, which solves the problem that the immersion effect is influenced by the easy generation of precipitation when the antioxidant liquid is immersed while improving the oxidation resistance of graphite, but does not specifically research whether the friction performance of graphite materials can be improved after immersion.

The performances of the impregnated graphite such as friction performance, mechanical property and the like have a larger relationship with the material properties of the impregnant, the impregnants commonly used for the impregnated graphite M106K and M106D at present are furan resin and metallic antimony, although the mechanical property and the friction performance of the graphite are greatly improved, the friction performance of the impregnated graphite is greatly reduced when the environmental temperature is increased, the friction coefficient is increased, and even the friction performance of the impregnated furan resin graphite at high temperature is inferior to that of the untreated graphite. In the aspect of an impregnation process, due to the influence of impregnation materials (furan resin and metal antimony), the traditional impregnation process needs to be carried out in a pressurized and high-temperature environment to ensure the impregnation effect, the requirements on impregnation equipment are high, a high-pressure tank is usually adopted, a heating system needs to be arranged, the impregnation equipment is complex, and the impregnation period is long. Impregnant raw materials and proportion thereof play a critical role in the working performance of impregnated graphite, and a novel high-efficiency impregnant and a normal-temperature and normal-pressure impregnation environment are an important direction for the development of impregnated graphite.

The novel impregnant provided by the invention can improve the tribological performance of the graphite material, expands the application range of the graphite material, and has great practical significance in saving energy and prolonging the service life of equipment.

Disclosure of Invention

The invention aims to overcome the defects of complex graphite impregnation process and poor friction performance in a high-temperature environment in the prior art, and provides an economical and simple preparation method for improving the friction performance of a graphite material at high temperature.

The invention provides a preparation method for improving the friction performance of a graphite material at high temperature, which comprises the following steps:

a method for improving the high-temperature friction performance of a graphite material and a preparation method thereof are characterized by comprising the following steps:

(1) and (4) preparing an impregnation liquid. Dissolving boric acid in solvent such as distilled water or absolute ethyl alcohol to prepare boric acid high-concentration solution as impregnation liquid;

(2) and (4) pretreatment of graphite flakes. Cleaning the surface of a graphite flake, and placing the graphite flake in an incubator for drying, wherein the drying temperature is 70-100 ℃, and the drying time is 2-5 hours;

(3) impregnation of graphite sheets: placing the pretreated graphite flakes in an impregnation kettle, pouring high-concentration boric acid impregnation liquid into the impregnation kettle to completely immerse the graphite flakes, fully stirring, standing, keeping the distance between the graphite flakes above 5 mm, and sufficiently impregnating for a long time;

(4) the impregnation solution is evaporated. Keeping the temperature for 2-20 hours at normal pressure or below 0.5MPa at normal temperature or low temperature, taking out the impregnated graphite flake after no obvious liquid exists in the impregnation kettle, and cleaning the surface;

(5) and (3) drying: and (3) putting the impregnated graphite flake into an incubator, setting the temperature to be 40-80 ℃, and carrying out heat preservation and drying.

The invention has the effects of improving the performance of the graphite material and improving the dipping process:

1) compared with the unimpregnated graphite, the mechanical property is obviously improved, the friction coefficient is reduced, and the abrasion loss is reduced;

2) compared with M106K and M106D graphite, the graphite has obviously improved temperature resistance, smaller friction coefficient at 120 ℃ and narrower grinding crack.

3) Compared with the traditional impregnation process of the graphite M106K and M106D, the method provided by the patent has the advantages that the conditions are easier to achieve, the pressure is not required in the impregnation process, and the required temperature is not more than 100 DEG C

Drawings

FIG. 1 is a flow chart of a method for preparing a graphite material with improved high-temperature friction performance.

FIG. 2 is a comparison of the coefficient of friction of example 1 versus unimpregnated graphite over time under load at ambient temperature.

FIG. 3 is a comparison of the friction coefficient of example 1 and example 2 with time at room temperature under a low load.

FIG. 4 is a comparison of the surface topography before and after the rub test of example 1 with non-impregnated graphite at 120 ℃.

In fig. 4: a) before friction without impregnated graphite, b) after friction without impregnated graphite, c) before one time of impregnation friction, d) after one time of impregnation friction

FIG. 5 is a comparison of the coefficient of friction of example 1 versus unimpregnated graphite over time at 120 ℃.

FIG. 6 is a comparison of the surface topography before and after rubbing experiments with M106K and M106D of example 2 at 120 ℃.

In fig. 6: a) before three times of impregnated graphite rubbing, b) after three times of impregnated graphite rubbing, c) before M106K rubbing, d) after M106K rubbing, e) before M106D rubbing, f) after M106D rubbing

FIG. 7 is a comparison of the friction coefficient of example 2 with that of M106K and M106D as a function of time at 120 ℃.

Detailed Description

The present invention is described in detail below with reference to specific examples so that those skilled in the art can better understand the present invention and can practice the present invention, but the present invention is not limited to the scope of the examples.

Example 1:

(1) and preparing boric acid impregnation liquid. The solution can be selected from distilled water, absolute ethyl alcohol and the like, preferably absolute ethyl alcohol, and the mass ratio of the boric acid powder to the absolute ethyl alcohol is 1: 5, preparing a supersaturated solution of boric acid and absolute ethyl alcohol as a soaking solution;

(2) pre-treating graphite flakes. Cleaning the surface of a graphite flake, and placing the graphite flake in an incubator for drying, wherein the drying temperature is set to 80 ℃, and drying is carried out for 2 hours;

(3) impregnating the graphite sheet. Placing the pretreated graphite flakes in an impregnation kettle, pouring the boric acid-absolute ethyl alcohol supersaturated impregnation liquid into the impregnation kettle to completely immerse the graphite flakes, uniformly stirring, keeping the distance between the graphite flakes to be more than 5 mm, and impregnating for 24 hours;

(4) the impregnation solution is evaporated. Under normal pressure, keeping the temperature in the kettle at 55 ℃, taking out the impregnated graphite flake after no obvious liquid exists in the impregnating kettle, and cleaning the surface;

(5) and (3) drying: the impregnated graphite flakes were placed in an incubator at a set temperature of 50 ℃ and dried after 2 hours of incubation.

Example 2:

(1) and preparing boric acid impregnation liquid. The solution can be selected from distilled water, absolute ethyl alcohol and the like, preferably absolute ethyl alcohol, and the mass ratio of the boric acid powder to the absolute ethyl alcohol is 1: 5, preparing a supersaturated solution of boric acid and absolute ethyl alcohol as a soaking solution;

(2) pre-treating graphite flakes. Cleaning the surface of a graphite flake, and placing the graphite flake in an incubator for drying, wherein the drying temperature is set to 80 ℃, and drying is carried out for 2 hours;

(3) impregnating the graphite sheet. Placing the pretreated graphite flakes in an impregnation kettle, pouring the boric acid-absolute ethyl alcohol supersaturated impregnation liquid into the impregnation kettle to completely immerse the graphite flakes, uniformly stirring, keeping the distance between the graphite flakes to be more than 5 mm, and impregnating for 24 hours;

(4) the impregnation solution is evaporated. Under normal pressure, keeping the temperature in the kettle at 55 ℃, taking out the impregnated graphite flake after no obvious liquid exists in the impregnating kettle, and cleaning the surface;

(5) and (3) drying: putting the impregnated graphite flake into a heat preservation box, setting the temperature to be 50 ℃, preserving the heat for 2 hours and drying;

(6) the impregnation was repeated. And (5) repeating the steps (3) to (5) to obtain the impregnated graphite sheet which is impregnated for three times.